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Oral Maxillofac Surg6:1426-1438, 2008

Anatomical and Surgical Findings andComplications in 100 Consecutive

Maxillary Sinus FloorElevation Procedures

Steven A. Zijderveld, DDS, MD,*

Johan P.A. van den Bergh, DDS, PhD,†

Engelbert A.J.M. Schulten, DDS, MD, PhD,‡ and

Christiaan M. ten Bruggenkate, DDS, MD, PhD§

Purpose: To investigate the prevalence of anatomical and surgical findings and complications inmaxillary sinus floor elevation surgery, and to describe the clinical implications.

Patients and Methods: One hundred consecutive patients scheduled for maxillary sinus floor eleva-tion were included. The patients consisted of 36 men (36%) and 64 women (64%), with a mean age of50 years (range, 17 to 73 years). In 18 patients, a bilateral procedure was performed. Patients weretreated with a top hinge door in the lateral maxillary sinus wall, as described by Tatum (Dent Clin NorthAm 30:207, 1986). In bilateral cases, only the first site treated was evaluated.

Results: In most cases, an anatomical or surgical finding forced a deviation from Tatum’s standard proce-dure. A thin or thick lateral maxillary sinus wall was found in 78% and 4% of patients, respectively. In 6%, astrong convexity of the lateral sinus wall called for an alternative method of releasing the trapdoor. The samemethod was used in 4% of cases involving a narrow sinus. The sinus floor elevation procedure was hinderedby septa in 48%. In regard to complications, the most common complication, a perforation of the Schneide-rian membrane, occurred in 11% of patients. In 2%, visualization of the trapdoor preparation was compromisedbecause of hemorrhages. The initial incision design, ie, slightly palatal, was responsible for a local dehiscence in 3%.

Conclusion: To avoid unnecessary surgical complications, detailed knowledge and timely identificationof the anatomic structures inherent to the maxillary sinus are required.© 2008 American Association of Oral and Maxillofacial Surgeons
J Oral Maxillofac Surg 66:1426-1438, 2008
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axillary sinus floor elevation with autogenous orynthetic grafting material has proven to be a reliableethod that enables the insertion of endosseous im-lants in patients with a severely resorbed maxilla.

*Oral and Maxillofacial Surgeon, Department of Oral and Maxil-

ofacial Surgery, Free University Medical Center/Academic Center

or Dentistry Amsterdam, Amsterdam, and St Antonius Hospital,

ieuwegein, The Netherlands.

†Oral and Maxillofacial Surgeon, Department of Oral and Maxil-

ofacial Surgery, Free University Medical Center/Academic Center

or Dentistry Amsterdam, Amsterdam, and St Antonius Hospital,

ieuwegein, The Netherlands.

‡Associate Professor, Department of Oral and Maxillofacial Sur-

ery, Free University Medical Center/Academic Center for Den-

istry Amsterdam, Amsterdam, The Netherlands. d

1426

he classical sinus floor elevation consists of a topinge door in the lateral maxillary sinus wall, as

nvented by Tatum,1 but first described by Boynend James 1980.2 The variety of anatomical modal-

§Professor, Department of Oral and Maxillofacial Surgery,

ree University Medical Center, Academic Center for Dentistry

mterdam, Amsterdam, and Rijnland Hospital, Leiderdorp, The

etherlands.

Address correspondence and reprints requests to Dr Zijderveld:

epartment of Oral and Maxillofacial Surgery, St Antonius Hospital,

oekoekslaan 1, 3435 CM Nieuwegein, The Netherlands; e-mail:

[email protected]

2008 American Association of Oral and Maxillofacial Surgeons

278-2391/08/6607-0016$34.00/0

oi:10.1016/j.joms.2008.01.027

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ZIJDERVELD ET AL 1427

ties in the shape of the inner aspect of the maxil-ary sinus defines the surgical approach.3 Van denergh et al described a number of anatomical con-iderations.3

Several studies described separate anatomical find-ngs, such as blood supply to the lateral wall, sinushape, and sinus septa4-11 (Table 1). To the best of ournowledge of the literature, this is the first prospec-ive study with regard to most of the anatomicalndings during 100 consecutive maxillary sinus floorlevation procedures. To avoid unnecessary surgicalomplications, detailed knowledge and timely identi-cation of the anatomic structures inherent to theaxillary sinus are required. The aim of the present

tudy was to investigate the prevalence of differentnatomical findings and complications in maxillaryinus floor elevation procedures, and to describe thelinical implications.

atients and Methods

For this prospective study, 100 consecutive pa-ients scheduled for maxillary sinus floor elevationere included. The patients consisted of 36 men

36%) and 64 women (64%), with a mean age of 50ears (range, 17 to 73 years). In 18 patients, a bilateralrocedure was performed. All sinus floor elevationsere performed by the same surgeon.Only the first unilateral site was evaluated accord-

ng to the anatomical findings and complications. Allatients were treated in the Department of Oral andaxillofacial Surgery, Free University Medical Center

Amsterdam, The Netherlands), or at the Rijnlandospital (Leiderdorp, The Netherlands). Directly afterach sinus floor elevation procedure, a standardhecklist was filled out, according to predefined cri-eria.

Patients were treated with a sinus floor elevationechnique according to Tatum, ie, an osteotomy ofhe lateral wall of the maxillary sinus.1 Patients treatedith a less invasive surgical approach for maxillary

inus elevation (the transalveolar approach, as de-cribed by Summers12) were excluded from thistudy.

In cases with a bilateral procedure, it was decidedo evaluate only the first unilateral site. Patients werevaluated according to anatomical findings, with sur-ical relevance related to the maxillary sinus floorlevation, and to complications. Anatomical findingsuch as septa or perforations could only be countednce per patient. Surgical observations that called fornforeseen and additional measurements, such asembrane perforations or hemorrhages, were also

ounted as complications, regardless of eventual heal-ng. In regard to complications, the follow-up period

as restricted to an osseointegration time of 3 c

onths after implant placement, and in this study, nobservations were performed subsequent to implantailures.

esults

In most cases, an anatomical or surgical findingorced a deviation from the standard procedure ofatum.1 A thin or thick lateral maxillary sinus wallas found in 78% and 4% of patients, respectively.In these cases, the initial trapdoor preparation dif-

ered. The lateral wall was defined as thin if, aftereflection of the mucoperiosteum, the Schneiderianembrane already shone dark grayish-bluish through

he sinus wall. A maxillary sinus wall was consideredhick if it measured at least 2.3 mm, which was similaro the diameter of the stainless steel burr.

In cases of strong convexity of the lateral maxillaryinus wall, the inward and upward rotation of theractured door can easily lead to a mucosa tear at theranially placed trapdoor osteotomy. If the authorsbserved this risk factor when releasing the trapdoor,he lateral wall was scored as “convex.”

In 6% of patients, a strong convexity of the lateralinus wall called for an alternative method of releasinghe trapdoor. The same method was used in 4% ofatients with a narrow sinus. The prepared door wasonverted into a hatch, mobilized on four sides andarefully lifted upward. A wide sinus, observed in 7%f patients, may lead to underfilling, so that the esti-ated bone height appears not to be the true bone

eight, leading to perforation of the implant into theinus. The authors observed that the method of Tatum1

as hindered by septa in 48% of cases. Inversion of theone plate was complicated by these septa. The septaere left intact, and the contour of the sinus was fol-

owed by making a W-shaped trapdoor preparation or 2eparated doors. In 5 cases, this alternative procedureesulted in a membrane perforation at the location of theepta. The perforations were then covered with aesorbable barrier membrane, and because of thisroper surgical measurement, the perforations had noegative effect on the eventual outcomes of the proce-ures. In all 5 cases, the healing was not compromised.he prevalences of different anatomical findings are

isted in Table 2. We found no significant differencesith regard to gender or age.With regard to complications, the most common

omplication, perforation of the Schneiderian mem-rane, occurred in 11% of patients. As already men-ioned, 5 perforations occurred in relation to septa, and

additional perforations were the result of extensionesially when releasing the Schneiderian membrane,

ecause of poor visibility. The direct connection be-ween the sinus and oral mucosa was the cause in one
ase of a membrane perforation, occurring directly after

Table 1. ANATOMICAL STUDIES AND FINDINGS IN RELATION TO SINUS FLOOR AUGMENTATION PROCEDURES

Reference N Purpose Study Design Conclusions

Ulm et al, 199516 41 Prevalence and localization of septa Cadaver study Prevalence 31.7%Most septa (73.3%) in bicuspid region

Krennmair et al, 199718 65 Prevalence of septa Clinical examination Prevalence 27.7%200 Morphology of septa CT scan Prevalence 16.0%

Significantly greater dimension of septa in nonatrophicmaxillary regions

Krennmair et al, 19999 194 Prevalence and location of septa CT scan versuspanoramic x-ray

Prevalence significantly greater in atrophic maxillae thanin dentate regions

Panoramic x-ray less sensitive and specific than CT scanVelasquez-Plata et al, 200222 312 Prevalence and morphology of

septaCT scan Prevalence 24%, prevalence significantly greater in

edentulous maxillas; most in middle region, at meanheights of 7.59, 5.89, and 3.54 mm in lateral, middle,and medial areas, respectively

Kim et al, 200620 100 Prevalence and morphology ofsepta

CT scan Prevalence, 26.6%; 50.8% in the middle region; meanheights of 1.63, 2.44, and 5.46 mm in lateral, middle,and medial areas, respectively

Cho et al, 200117 59 Influence of sinus anatomy onmembrane perforation

CT scan in correlationwith experiencedperforation rate

Perforation most frequently in narrow sinus

Proussaefs et al, 200427 24 Effect of repair on perforated sinusmembrane

Human study, split-mouth design,histomorphometry

Perforated sites result in reduced bone formation inrelation to nonperforated sites (33.5% vs 14.1%), andreduced implant survival rates (69.5% vs 100%)

Shlomi et al, 200425 73 Incidence of membrane perforationand influence on clinicaloutcomes

Clinical andradiographic

Incidence of 28%, no statistically significant difference insurvival rate (90% vs 91% in control group) and ridgeheight pre- and postsurgery

Ardekian et al, 200628 110 Significance of membraneperforation

Clinical Incidence of 32%, more frequently with low height ofresidual ridge, no difference in success rates

Solar et al, 19995 18 Examination of vascularization ofthe lateral maxilla

Cadaver study Prevalence of intraosseous artery lateral maxilla, 100%;mean distance between intraosseous anastomosis inlateral maxilla and alveolar ridge, 19 mm

Elian et al, 20054 50 Distribution of maxillary artery CT scan, intraosseousartery of lateralmaxilla

Prevalence of 52%, mean distance of 16 mm fromalveolar crest

Uchida et al, 19987 38 Measurement of sinus volumes forbone grafting

CT scan and sinusfloor simulation

Mean volume of inferior portion of the sinus, 4.02 cm3

for 15-mm lifting, and 6.19 cm3 for 20-mm lifting

Abbreviation: CT, Computed tomography.

Zijderveld et al. Complications in Maxillary Sinus Floor Elevation Procedures. J Oral Maxillofac Surg 2008.

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eflection of the mucoperiosteum. Fortunately, this per-oration remained relatively small. In 1 perforation, nonatomical explanation could be given. The perforationsere all covered with a barrier membrane, and the

ventual healing was uneventful.In 2% of patients, visualization of the trapdoor prep-

ration was compromised because of hemorrhages. Inur study group, only 1 patient developed postoper-tive maxillary sinusitis. This patient had no preoper-tive risk factors, such as sinus pathology in the past,or a perioperative perforation of the Schneiderianembrane.The initial incision design, ie, slightly palatal, was

esponsible for local dehiscence in 3% of patients. In 2atients with local wound dehiscence, graft infectionas observed along with a purulent discharge, and was

reated by antibiotic therapy and local debridement. Theehiscence healed by secondary granulation.At the time of implantation in 1 patient, the sinus

avity was reached after drilling to a depth of 8 mm,ndicating a partial loss of the graft. This patienthowed no signs of infection, and in particular, noaxillary sinusitis in the time of healing after eleva-

ion. As an alternative explanation for this finding, thechneiderian membrane was probably not elevated asar as the medial wall, resulting in underfilling withraft material of the created space.

Table 2. ANATOMIC FINDINGS IN 100CONSECUTIVE MAXILLARY SINUS FLOORELEVATION PROCEDURES

hin lateral sinus wall 78%hick lateral sinus wall 4%onvex lateral sinus wall 6%onnection of Schneiderian membrane andoral mucosa 2%arrow sinus 4%ide sinus 7%

inus septa 48%ongitudinal sinus septum 2%oot-shape configurations 4%

ijderveld et al. Complications in Maxillary Sinus Floor Elevationrocedures. J Oral Maxillofac Surg 2008.

Table 3. COMPLICATIONS IN 100 CONSECUTIVEMAXILLARY SINUS FLOOR ELEVATION PROCEDURES

erforation of Schneiderian membrane 11%erioperative hemorrhages 2%ostoperative hemorrhages 0%ostoperative maxillary sinusitis 1%ocal wound dehiscences 3%raft infections 2%oss of graft 1%oss of implants 4%

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In 4 different patients, 4 implants were lost duringhe osseointegration period of 3 months. In a total of43 implants placed, this was equivalent to 1.6%. Weould not find any relationship to the remaining crest

IGURE 1. Pneumatization of maxillary sinus after tooth loss,robably caused by reinforcement of osteoclastic activity of thechneiderian membrane.


IGURE 2. A, In cases of a thin maxillary sinus wall, after reflec-ion of the mucoperiosteum, the Schneiderian membrane alreadyhines a dark grayish-bluish through the lateral sinus wall. B, Theateral door preparation is made directly with a round diamondurr, without use of a stainless-steel burr.


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1430 COMPLICATIONS IN MAXILLARY SINUS FLOOR ELEVATION PROCEDURES

f the native maxilla. In none of these patients did anyther complication, as mentioned in this study, occur.omplications are listed in Table 3.

iscussion

ANATOMICAL FINDINGS

Thin or Thick Lateral Maxillary Sinus WallAfter loss of the maxillary teeth and reduction of theasticatory forces acting on the maxilla, the sinus wall

radually becomes thinner as a result of the increasedize (or volume) by pneumatization of the maxillaryinus.13 The duration of edentulism is decisive for thextent of alveolar-ridge resorption and antral pneumati-

IGURE 3. Schematic drawing of the thinning out of a thick lateralall for the purpose of a good visualization of the inner aspect of

he bony sinus.


FIGURE 4. A profound convexity of the maxillary sinus

ijderveld et al. Complications in Maxillary Sinus Floor Elevation Proc

ation of the alveolar process.14 Increased antral pneu-atization starting after tooth loss seems to result espe-

ially from the basal bone loss caused by aeinforcement of osteoclastic activity of the Schneide-ian membrane (Fig 1).15 In extreme cases, only a paper-hin lamella of bone separates the maxillary sinus fromhe oral cavity after long-term edentulism.16

In cases of a very thin maxillary sinus wall, carefuleflection of the mucoperiosteum is recommended,hile the Schneiderian membrane already shines dark

rayish-bluish through the sinus wall (Fig 2A). Reflec-ion of the mucoperiosteum with sharp instrumentsan already cause a perforation of the sinus wall andhe Schneiderian membrane. In the present study,fter reflection of the mucoperiosteum, this transpar-nt, dark aspect was observed in 78% of cases. Be-ause of the risk of perforation of the Schneiderianembrane during lateral door preparation in these

ases, it is advised not to begin the lateral door prep-ration with a round stainless-steel burr, but to use aound diamond burr directly, and thus reduce the riskf a membrane perforation (Fig 2B).If the lateral wall consists of thick bone, the whole

ateral wall should be thinned out (Fig 3). When thetainless-steel burr, with a diameter of 2.3 mm, totallylled the lateral osteotomy (Fig 3), this alternativerocedure was followed. Otherwise, it would be ex-remely difficult to mobilize the Schneiderian mem-rane from the inner aspect of the bony sinus, be-ause instruments cannot reach this tissue due to aeep cleft-like approach.3

Convex Lateral Sinus WallIn 6% of the patient population in this study, the

onvexity of the lateral maxillary sinus wall called for

metimes required an alternative trapdoor preparation.
wall so
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n alternative trapdoor luxation (Fig 4). In normalases, the procedure consists of the preparation of aop hinge door in the lateral maxillary sinus wall. Inases of a convex lateral sinus wall, the inward andpward rotation of the fractured door can easily leado a mucosa tear at the cranially placed trapdoor

IGURE 5. A, Patient with a convexity of the lateral sinus wall. B,he prepared door was mobilized on 4 sides and lifted upward.


IGURE 6. Perforation immediately after reflection of the mucope-iosteum, because of direct contact of the sinus mucosa with theral mucosa.

pijderveld et al. Complications in Maxillary Sinus Floor Elevationrocedures. J Oral Maxillofac Surg 2008.

steotomy. Therefore, in cases of profound convexityf the maxillary sinus wall, an alternative approach isdvisable, in which the prepared door is converted to

hatch, mobilized on 4 sides and carefully liftedpward to a horizontal position in the maxillary sinusFigs 5A,B). Alternatively, the trapdoor preparationan be placed medial to the convexity of the lateralinus wall, tunneling farther in a distal direction, al-hough this creates a higher risk of perforating thechneiderian membrane.

Connection Between the SchneiderianMembrane and Oral MucosaWhen the alveolar bone is totally absent in some

laces (because of resorption or traumatic bone lossfter tooth extraction, eg, sinus perforation), the sinusucosa may be in immediate contact with the oralucosa. This is a very difficult condition, in which the

chneiderian membrane cannot usually be kept intactFig 6). It may lead to large perforations at very diffi-ult sites, making any further preparation impossi-le.3

Previous sinus surgery (eg, a Caldwell-Luc proce-ure) sometimes constitutes a contraindication foraxillary sinus floor elevation, because anatomical

isconfigurations do not allow for the preparation ofntact, healthy mucosal tissue (Fig 7). In cases ofrevious sinus operations, a preoperative computedomography (CT) scan can be helpful in demonstrat-ng this condition.

The Narrow and Wide SinusUntil the eruption of permanent teeth, the sinus

avities are insignificant in size. The development ofhe maxillary sinus is a dynamic, active procedurehen 2 conditions apply: a slight, positive intrasinus

IGURE 7. Absence of the lateral maxillary sinus wall, because ofrevious sinus surgery (a Caldwell-Luc procedure). This is a contra-

ndication for sinus floor elevation. R, right; P, posterior.


ressure, and good physiology of the mucosal sinus

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embrane, which should be supple and easy to ex-and, as well as capable of bone resorption and thin-ing the sinus wall. This is in line with the presencef osteoclasts found in the maxillary sinus, as thesteoclastic activity is jointly responsible for the re-orption and thinning of the sinus wall.15

There is a wide range in sizes and shapes of max-llary sinuses. In a study by Uchida et al,7 maxillaryinus volumes were measured using CT images of 38inuses and a 3-dimensional reconstruction system.he average total maxillary sinus volume was 13.6 �.4 cc. The minimum maxillary sinus volume was 3.5c, and the maximum was 31.8 cc.7

The size of the sinus, and especially the angulationetween the medial and lateral walls of the maxillaryinus, seemed to exert a large influence on the inci-ence of membrane perforation during maxillary si-us floor elevation. The sharper angles observed athe inner walls of the sinus at the sites of the secondpper bicuspid presents a higher risk of perforation.he angulation will influence the feasibility of theinus floor during elevation. Group 1 of Cho et al17

onsisted of specimens with an angle of 30° or less,roup 2 consisted of specimens with angles between1° and 60°, and group 3 consisted of specimens withngles of 61° or greater. The different groups demon-trated significant correlation with the observed per-orations. The perforation rates were 37.5% (group 1),8.6% (group 2), and 0% (group 3).17 The sites of therst upper molars are the least difficult areas.8,17 Inhe present study, 4 patients had a narrow maxillaryinus that required an alternative surgical approach.

The most reliable method in terms of being preop-ratively informed about the size and shape of theaxillary sinus is a CT scan. With a preoperative CT

can, a narrow maxillary sinus can be anticipated.ne way to circumvent the problem of a narrow sinus

s by performing an antrostomy in the lateral wallnstead of a door preparation. In this situation, how-ver, the sturdy bone support and a new floor of theinus will be absent, and the one bone-inductive ele-ent for the bone graft will fail. Alternatively, therepared door can be converted into a hatch, mobi-

ized on all 4 sides and carefully lifted (pedunculatednly to the sinus mucosa) upward to a higher position

n the maxillary sinus, where the lateral sinus dimen-ions are larger (Figs 8A,B).3 In such cases, it is ad-ised to make an all-around preparation, to minimizehe risk of perforating the Schneiderian membrane. Inll 4 cases in the present study, this alternative surgi-al method was chosen.In cases of a wide maxillary sinus, it is recom-ended to make a large door preparation, and lift the

oor to a high position cranially. However, without areoperative CT scan, the surgeon is mostly unin-

ormed about this possibility. Especially in a wide a

inus, there is a risk of underfilling the recipient siteith grafting material if elevation of the membraneas not been continued as far as the medial wall. Thisnderfilling might lead to later complications, if thestimated bone height appears not to be the trueone height during implant surgery, leading to perfo-ation of the implant into the sinus (Fig 9).

Maxillary Sinus SeptaThe presence of septa increases the risk of sinusembrane perforation during sinus floor elevationrocedures. This anatomic variation was first de-cribed by Underwood in 1910,11 and therefore isometimes referred to as Underwood’s septa. In an

IGURE 8. Axial computed tomography scan (A) and schematicrawing (B) of the narrow maxillary sinus. The prepared door cane converted into a hatch, mobilized on all 4 sides, and carefully

ifted (pedunculated only to the sinus mucosa) to a higher positionn the maxillary sinus. Arrows indicate the direction in which therapdoor should be displaced.


natomical study, Underwood11 found 30 septa in 90

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axillary sinuses, showing a prevalence of 33%. Thencidence of antral septa varies between 16% and8%.9 The prevalence of septa was significantlyreater in atrophic edentulous regions than in dentateegions. Krennmair et al9,18 hypothesized that if teethre gradually lost, atrophy begins at different times inifferent regions. They classified septa into primarywhich arise from the development of the maxilla)nd secondary (which arise from irregular pneumati-ation of the maxillary sinus floor after tooth loss).ecause maxillary molars are often lost earlier thanre premolars, the different phases of maxillary sinusneumatization result in the formation of antral septa.ence Krennmair et al9,18 stated that 70% of antral

epta were found in the anterior region. Stover criti-ized these conclusions, stating a greater prevalencef septa in the posterior segments results from rem-ant interradicular bone between adjacent maxillaryolars.19

The prevalence of primary septa was found to beignificantly higher.9,20-22

The average height of medial insertions was greaterhan that of the lateral insertions. In other words,eptal height increased from lateral to medial inser-ions. This can complicate the inversion of the bonelate or lateral door.Panoramic radiography has less sensitivity and

pecificity than CT scanning for the detection of sinusepta (Fig 10). Krennmair et al9 reported a false-ositive or negative diagnosis regarding the presencef antral septa in 21.3% of cases.In instances where septa are encountered on the

inus floor, Boyne and James2 recommended cuttinghem with a narrow chisel and removing them with aemostat, so that the bone graft can be placed over

IGURE 9. In a wide sinus, seen on this axial computed tomogra-hy scan, there is a risk of underfilling if the elevation of theembrane has not been continued as far as the medial maxillary

inus wall.


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ony wall into an anterior and a posterior part of theinge door, and inverted both trapdoors.The present authors suggest following the contour

f the sinus floor by making a W-shaped preparationn smaller septa, or 2 separate doors (Figs 11A-C).3

nother option would involve an antrostomy ap-roach.24

Longitudinal SeptumElevation of the Schneiderian membrane is a time-

onsuming procedure. In most cases, upon reachinghe floor of the maxillary sinus, visibility improves,ccelerating the procedure.

However, in 2 cases, a horizontal and longitudinalim was encountered, in mesiodistal or sagittal direc-ion instead of the usual transversal septa, halfwayetween the sinus floor and medial wall. Because ofhis unexpected rim, there was a risk of perforatinghe membrane while shooting out with an elevationnstrument. In contrast to a root-shape configuration,his rim is located along the full length of the sinusoor (Fig 12).

Root-Shape ConfigurationsRoot-shape configurations, found in 4 patients of

he study group, can be expected when teeth haveeen extracted recently (Fig 13). In 2 of 4 cases, theeparation of the Schneiderian membrane caused aerforation at this particular location. If possible, si-us floor elevation should be delayed for at least 6onths after extraction of the teeth when root-tip

xpressions in the maxillary sinus are clearly visiblen a panoramic radiograph.

IGURE 10. The coronal computed tomography scan has a highensitivity and specificity for the detection and localization of sinusepta.


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SURGICAL FINDINGS

Maxillary Sinus-Membrane PerforationSinus-membrane perforation is the most prevalent

omplication of sinus floor elevation procedures (10%o 60%).25-28 Anatomic as well as technical factorsave been implicated in membrane perforation. The

ntegrity of the sinus membrane is essential in main-aining the healthy, normal function of the maxillaryinus. The mucociliary apparatus protects the sinusgainst infection by removing organisms trapped inucus through the ostium. The membrane also acts

s a biologic barrier, and an increased chance ofnfection results if the biologic barrier (the mem-rane) perforates because a greater number of bacte-ia can invade the graft. Possible causes of perforationnclude tearing of the membrane during window os-eotomy or with an infracture of the bony window,levation of the membrane, the presence of septa,nd overfilling with graft material.26 Documented riskactors include irregularities of the sinus floor, rootormations, previous sinus surgery (scar tissue), and

lower height of the residual alveolar crest.3,28

rdekian et al28 reported that in residual ridges of 3m, a perforation of the sinus membrane occurred

IGURE 11. A, B, The suspected sinus septa on the antral floor ischneiderian membrane is at risk of being torn, particularly at the c

ijderveld et al. Complications in Maxillary Sinus Floor Elevatio

n 85% of cases, whereas in residual ridges of 6 mm, s

perforation was observed in 25% of cases. In mosttudies, no statistical difference was observed inhe success rates of implants placed with sinusone grafting in patients whose Schneiderian mem-rane was perforated versus those patients inhom the membrane remained intact. However, aistomorphometric study according to a split-mouthesign, and with regard to sinus perforation duringurgery, suggested that repairing the perforated sitef the sinus membrane with a resorbable collagenembrane may result in reduced bone formation andreduced implant survival rate.25 When the perfora-

ion is small (�2 mm) and located in an area wherehe elevated membrane is folded together, it will healy itself. However, even with a small perforation or aery thin Schneiderian membrane, the present au-hors prefer to use a resorbable collagen membrane toover and support the weak spot. Larger perforationsre almost always managed by the use of a barrierembrane. In the present study, a freeze-dried human

amellar bone sheet (Lambone; Pacific Coast Tissueank, Los Angeles, CA) was applied after it washaped and cut for proper fit. The large size of a sheets chosen to provide a customized fit within the bony

itu and visualized by making 2 trapdoors. C, When elevated, thedge of the septum. A membrane is placed to cover the perforation.


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inus walls. The corners are rounded off, and the

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embrane is rehydrated before placement in theaxillary sinus (Figs 14A-C). Other treatment options

nclude the use of an autogenous block graft insteadf a cancellous graft, suturing, or abandonment of theurgical procedure.

With regard to the prevention of a perforation, theresent authors make some additional small holes inhe suction device, to diminish the suction power.urthermore, the prevention of direct contact of theuction device with the Schneiderian membrane cane achieved by placing an elevation instrument be-ween them.

HemorrhagesKnowledge of the blood supply to the maxillary

inus is of importance in sinus floor elevation proce-ures, in terms of both vascularization of the sinusraft and the location of that blood supply relative tohe position of the required lateral osteotomy. Theurgical severance of one of the vessels may not be aife-threatening event, but may complicate the proce-ure, because of the more difficult visualization of thechneiderian membrane. Although the maxilla is veryensely vascularized in young and dentate popula-ions, the blood supply to the bone is permanentlyeduced with age and progressing atrophy, and theumber of vessels and their diameters decrease, whileortuosity increases.4 Three arteries supply the max-llary sinus: the posterior superior alveolar, infraor-

IGURE 12. Schematic drawing of a longitudinal or sagittal sep-um, instead of the usual transversal septum, of the antral floor.ecause of this unexpected rim, there is a risk of perforating theembrane while shooting out with an elevation instrument.


ital, and posterior lateral nasal arteries, all of whichZP

re ultimate branches of the maxillary artery. Theosterior superior alveolar artery supplies the liningf the antrum, posterior teeth, and superficialranches to supply the maxillary gingivae and muco-eriosteum. The dental branch of this artery courses

ntraosseously, halfway up the lateral sinus wall, andorms a horizontal anastomosis with the infraorbitalrtery. The infraorbital artery runs through the infra-rbital canal and, before emerging from the infra-rbital foramen, it gives off 1 or 2 branches thatourse caudally along the anterior antral wall.29 Anntraosseous anastomosis was found in all specimensn an anatomic study of cadavers, and was visualizedn 53% of the CT scans in a radiographic study.4,5 Inhe 2 studies, the mean distance of the intraosseousnastomosis to the alveolar crest was 19 mm and 16m, respectively. If the goal is to place implants 12m in length, the superior osteotomy cut will beade approximately 14 mm from the alveolar crest.ccording to CT scan data, 80% of the arteries are

ocated more than 15 mm from the crest, and are ato risk regarding a potential surgical complication.4

ut in cases where the alveolar ridge has been se-erely resorbed, the vessel will be closer to the cresthan the reported average.

In the present study, a hemorrhage during prepa-ation of the trapdoor was encountered in 2 patientsFig 15). In both patients, it reduced the visualizationnd hindered the surgical procedure, but had no nega-ive influence on the treatment outcome. Bleeding cansually be controlled by pressure with a mist gauze pad.

IGURE 13. Schematic drawing of dental root-shape configura-ion that makes preparation of the membrane difficult.


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lectrocautery should be avoided, because there is a riskf perforating the Schneiderian membrane.Solar et al5 reported on an extraosseous anastomo-

is of the same arteries mentioned in 44% of the cases.t is located at a mean distance of 23 mm from thelveolar ridge. The anastomosis is in close contactith the bone. Vertical incisions should therefore

xtend cranially as little as possible, and the perios-eum should be prepared with the utmost care, toinimize vascular trauma.In addition to anastomosis in the lateral wall of theaxillary sinus, a third artery can be a potential risk

or severing an intraosseously located artery during aigorous curettage for sinus elevation in the posterioredial wall of the sinus. The posterior lateral nasal

rtery can be found close to, or within, the medialall of the sinus, and because of the proximity of the

phenopalatine artery, it may produce a problematicow of blood if severed.6

Another form of perioperative or postoperativeleeding that can occur is an epistaxis, indicating aembrane perforation.

Postoperative Maxillary SinusitisThe rather low complication rate of 1% for postop-

IGURE 14. A, Patient with a perforation of the Schneiderian meeing shaped and cut for proper fit. C, The recipient side was filled

ijderveld et al. Complications in Maxillary Sinus Floor Elevatio

rative maxillary sinusitis is somewhat surprising. AZP

ransient or persisting effect on the ciliated antralucosa would be expected as a result of maxillary

inus floor elevation raising the Schneiderian mem-rane. When the maxillary sinus is filled with blood, aelay of maxillary sinus clearance is thought to occur,ecause it is generally assumed that a reduction of theatency of the osteomeatal unit creates a potential

. B, A freeze-dried human lamellar bone sheet was applied afterparticulated autogenous bone graft from the retromolar trigonum.


IGURE 15. Hemorrhages during preparation of the trapdooreduced the visualization and hindered the surgical procedure.

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isk for the development of maxillary sinusitis. How-ver, the results of a human study by Timmenga et al30

n regard to the effects of maxillary sinus floor elevationn maxillary sinus physiology suggest that the maxillaryinus mucosa is capable of adapting adequately to thehanges induced by elevation procedures, especiallyn cases of noncompromised sinus clearance.

Local Wound DehiscencesIn 3 cases, a local wound dehiscence occurred in

he first 2 weeks postoperatively. This was probablyecause, in the first treated patients, the incision onhe top of the crest was made slightly palatal (Figs6A,B). The main course of the supplying arteries isrom posterior to anterior, the main vessels run par-llel to the alveolar ridge in the vestibulum, and therestal area of the edentulous alveolar ridge is cov-red by an avascular zone with no anastomosesrossing the alveolar ridge. This argues in favor ofidline incisions on the alveolar ridge and avoidance

f incisions crossing the alveolar ridge, hence elimi-ating the risk of cutting anastomoses or cutting outvascular areas of the mucosa.31

The relatively low rate of complications in this

IGURE 16. A, The horizontal incision on top of the crest wasade slightly palatal. B, Postoperatively, a local wound dehis-ence occurred.


atient group was probably attributable to the perfor-2

ance of all procedures by 1 skilled surgeon. Inaxillary sinus floor elevation procedures, it is essen-

ial to have good knowledge of the different anatom-cal and surgical findings, to minimize perioperativend postoperative complications. The results of thistudy contribute to a better understanding of thisreimplant procedure.

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3. Tidwell JK, Blijdorp PA, Stoelinga PJ, et al: Composite graft-ing of the maxillary sinus for placement of endosteal im-plants. Int J Oral Maxillofac Surg 21:204, 1992

4. Bruggenkate CB, van den Bergh JPA: Maxillary sinus floorelevation a valuable pre-prosthetic procedure. Periodontology17:176, 2000

5. Shlomi B, Horowiz I, Kahn A, et al: The effect of sinus membraneperforation and repair with Lambone sheet on the outcome ofmaxillary sinus floor augmentation: A radiographic assessment. IntJ Oral Maxillofac Implants 19:559, 2004

6. Pikos M: Maxillary sinus membrane repair: Report of a tech-
nique for large perforations. Implant Dent 8:29, 1999
7. Proussaefs P, Lozada J, Kim J, et al: Repair of the perforatedsinus membrane with a resorbable collagen membrane: A hu-man study. Int J Oral Maxillofac Impl 19:413, 2004

8. Ardekian L, Oved-Peleg E, Mactei E, et al: The clinical sig-nificance of sinus membrane perforation during augmenta-tion of the maxillary sinus. J Oral Maxillofac Surg 64:277,2006

9. Traxler H, Windisch A, Geyerhofer U, et al: Arterial bloodsupply to the maxillary sinus. Clin Anat 12:417, 1999

0. Timmenga NM, Raghoebar GM, Liem RSB, et al: Effects ofaxillary sinus floor elevation surgery on maxillary sinus physi-ology. Eur J Oral Sci 111:189, 2003

1. Kleinheinz J, Buchter A, Kruse B, et al: Incision design inimplant dentistry based on vascularization of the mucosa. Clin
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